This invention relates generally to curable coating compositions comprising a polymerizable organosilicon compound and a polymerizable organic compound, and to a process for providing a substrate with a coating of a cured organosilicon compound. More specifically this invention relates to a coating process using novel, solventless silicone coating compositions which contain an organosilicon compound bearing (meth)acrylamide-substituted hydrocarbon radicals and certain organic vinyl compounds.
Colquhoun et al., U.S. Pat. No. 4,070,526, disclose radiation-curable coating compositions comprising a vinylic monomer, a mercaptoalkyl-containing siloxane compound and, optionally, a vinyl-containing siloxane compound. The vinylic monomer can be monofunctional or multifunctional and is said to be useful for varying the adhesive-releasing properties of the radiation-curable composition when it is coated onto a substrate and cured. However, the use of a vinylic monomer, whether monofunctional or multifunctional, with other types of silicone coating compositions, such as (meth)acrylamide-substituted organosilicon compounds, is not suggested.
Takamizawa et al., Japanese Publication No. 57-52371 (82-52371), disclose photosetting silicone compositions which contain a photosensitizer, certain (meth)acrylamide-containing siloxanes and, optionally, a solvent to reduce its viscosity. No examples of the solvent are disclosed and polymerizable diluents are not suggested.
Ansel et al., U.S. Pat. No. 4,496,210, disclose radiation-curable compositions for the coating of optical fibers. The compositions consist of certain ethylenically unsaturated siloxane compounds which have been narrowly defined so as to provide the cured composition with a certain modulus of elasticity. Specifically, the siloxane compound is limited to those containing a limited number of reactive side chains wherein the radiation-curable reactive sites thereof are monofunctional and have been derived from monofunctional side chains through the reaction of a radiation-curable compound therewith. Other materials, such as solvents, resins and radiation-curable monomers, can be incorporated into the composition. In particular, since patentees prefer ultraviolet light cure, liquid mono- or poly-acrylates may be added to adjust viscosity or for ancillary purpose. However, compositions comprising (meth)acrylamide-substituted organosilicon compounds are not suggested by this reference.
Varaprath, U.S. Pat. No. 4,608,270, discloses curable compositions which comprise di-(meth)acrylamide-substituted organosilicon compounds. These compositions are readily curable with heat or radiation and are said to be useful as comonomers with polymerizable vinyl monomers. Additionally, the curable compositions can also contain optional components which are commonly used in curable silicon-containing compositions. Examples of optional components are said to include solvents, polymerizable vinyl monomers, emulsion-forming components, colorants, stabilizers, fillers, adhesion promoters and surface modifiers. However, the use of specific organic vinyl compounds as polymerizable diluents is not suggested therein.
In view of the unusually high viscosity associated with organosiloxane polymers that contain di-(meth)acrylamide-substituted radicals it is desired to provide a way to reduce the viscosity of a coating composition prepared therefrom. Preferably, the coating composition should also not contain volatile materials that require additional equipment and/or processing steps for their containment and/or removal. Additionally, the composition should provide a coating that is not unfavorably altered by the particular means used to reduce the viscosity of the composition.